From the Publisher's Website:
Lost in Smaragdis is a pulp-style science fiction adventure RPG inspired by the lostrace, lost-world type stories of authors like H. Rider Haggard, Sir Arthur Conan Doyle, A. Merritt and Edgar Rice Burroughs.
Smaragdis, the Emerald World, is an alien yet earthlike planet inhabited by a collection of lost tribes and civilizations living in terror of dinosaurs and a tyrannical Conquistador kingdom. Scattered across Smaragdis are the relics of a vanished alien civilization - mysterious mind-gems that can grant strange powers but at the risk of madness, gangly robotic Demons, gigantic flying machines that can rain down lightning on command, and enigmatic monuments of stupendous scale that may hold the secrets of the cosmos. A portal in the Upper Amazon jungle can transport those who wander into it to Smaragdis, but if there are any portals leading back to Earth they have yet to be found.